Indoleninoxide, VI: Katalyse einer Isomerisierung durch Ethentetracarbonitril und Oxirantetracarbonitril

Indolenine Oxides, VI: Catalysis of an Isomerization by Ethenetetracarbonitrile and Oxiranetetracarbonitrile Ethenetetracarbonitrile ( 2 ) or oxiranetetracarbonitrile ( 7 ), when applied in quantities of 0.1 mol per mol of 1 , are effective in isomerizing the 3H ‐indole 1‐oxide 1 into the thermodynamically more stable lactam 4 in high yield. If either 2, 7 , or tetracyanoquinodimethan ( 8 ) are applied to 1 in 1:1 molar ratios, the yields of isomerization product 4 tend to drop. — A trivial acid catalysis brought about by contamination by acidic impurities may be excluded for the isomerization of 1 by 2 .